Block Acknowledgements (BLOCK ACK)
Rather than sending an individual acknowledgement following each data frame, 802.11n introduces a technique of confirming a burst of up to 64 frames using a single Block ACK (BA) frame. Block ACK even contains a bitmap to selectively acknowledge individual frames of a burst (comparable to selective TCP acknowledgements). The use of combined acknowledgments can be requested by sending a Block ACK Request (BAR). Block ACK options are negotiated and confirmed using Action frames defined in 802.11e (WLAN QoS).
Usage: AutoBA should be enabled by default. The only time when AutoBA should be disabled is when a decrease in performance and in stability with smart phones is identified.